1. Field of the Invention
The present invention relates generally to frozen carbonated beverage dispensing equipment, and more particularly to control and defrosting apparatus therefor.
2. Background of the Invention.
Frozen carbonated beverage machines are well known in the art, as seen, for example, in U.S. Pat. Nos. 3,608,779 and 3,460,713 to Richard T. Cornelius. Such equipment is designed to produce a slush beverage from the partial freezing of a combination of carbonated water and syrup. This confection is made by the continual harvesting thereof from the interior perimeter of a refrigerated cylinder.
Originally, frozen carbonated beverage machines were operated electro-mechanically. However, it was found that changes in ambient conditions, rate of beverage dispensing and the like, would have a great effect on the viscosity of the beverage, causing a drink to become either unacceptably loose or firm, as electro-mechanical systems would react too slowly or would overcompensate. Electronic controls are now used to provide for an improved ability to maintain the beverage viscosity within a predetermined desired range. As is known in the art, electronically pulsed expansion valves can provide for precise refrigeration control. Also, sensing the torque or power consumption of the motors that drive the harvesting mechanism provides an indication of the viscosity of the beverage. Thus, viscosity control is exerted through the use of electronically pulsed expansion valves operated in accordance with the sensed harvesting motor torque. However, scraper motors power requirement during a freezing cycle includes the resistance that results as the harvesting mechanism removes the portion of the newly semi-frozen beverage from the cylinder walls, as well as other factors normally present. Such factors include the frictional resistance that results from the mere contact between the harvesting mechanism and the cylinder interior, the drag caused by the beverage itself and that resulting from the motors and associated drive train components. Prior art machines have not been able to differentiate well between these variables. Thus, for example, during a freezing cycle harvesting load can be falsely interpreted to indicate that the beverage held in the cylinder has reached a desired firmness, whereupon refrigeration is stopped by turning off the compressor. However, if the beverage were not sufficiently firm, the sensed load would decrease rapidly as the stopping of refrigeration ends the production of further frozen beverage, hence the harvesting load associated therewith. Thus, refrigeration can be prematurely terminated, only to be quickly re-started, as the F.C.B. machine control was not able to differentiate between the contribution of the two load factors. This ineffective control ability results in deleterious short-cycling of the compressor.
A further problem with respect to viscosity control relates to the ease of operation of the F.C.B. machine. Prior art machines inevitably require fine tuning and precise adjustment of the electronic hardware thereof by trained service personnel. Such adjustments can be frequent and of substantial cost and inconvenience to the owner/operator who lacks the skill and knowledge necessary to attempt any direct manipulations of the machines electronics. Adjustment can be required due to changes in scraper motor load that can occur over time as the machine is used and various moving components, such as the harvesting mechanism, motor components and drive train, wear. Thus, if the load sensed on the motors does not compensate for such changes, the resulting beverage viscosity will also change over time for any given viscosity setting.
Repair of an F.C.B machine can also be costly due to the amount of technician time that can be required to diagnose the particular problem. Thus, it would be very desirable to have an F.C.B. machine wherein the various sub-components could be quickly and easily evaluated.
It is also known in the art that the refrigeration components of an F.C.B. machine can be placed in a remote location and connected to the dispensing portion by appropriate refrigeration and water lines. In this manner the over-the-counter portion utilizes less space in the retail area. However, a problem with such units having remote refrigeration concerns the heating and defrosting of the cylinders that is periodically required for the removal of particulate ice formation in the beverage, and for maintenance or cleaning of the cylinders. Hot gas can be cycled from the refrigeration system through the evaporator coils to provide for the defrosting. However, if the lines connecting the remote refrigeration unit to the cylinders are exposed to excessively cold ambient conditions, the hot gas may not be of sufficient temperature to provide for adequate defrosting when it reaches the evaporator coils. Thus, electrical heating of the cylinders has been used. These prior art heaters are generally tubular and lie adjacent and parallel to the cylinders and in direct contact with the evaporator coils. The cylinders and heaters are held within a cylinder box sub-structure, the void areas of which are filled with a foam insulation. If a heater should fail, repair of the cylinder box can be very costly as such repair necessitates the time consuming steps of removal of the cylinder box from the machine, removal of the insulation, replacement of the heater and, finally, re-insulating and replacement of the box in the machine. Therefore, it would be desirable to provide for easily replaceable electric heaters in an F.C.B. machine. It would also be desirable to have an F.C.B. machine that provides for improved monitoring and control of electrical defrost heaters to minimize any hazards associated with the operation thereof.